Kinetic Parameter Measurements in the CROCUS Reactor Using Current Mode Instrumentation

Pakari, Oskari; Lamirand, Vincent; Perret, G.; Frajtag, Pavel; Pautz, Andreas

doi:10.1109/tns.2018.2831180

Cited by 20 publications

(17 citation statements)

References 9 publications

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“…CROCUS has a recent history of neutron detector developments, such as fission chambers in current mode [20,21], fiber based miniature scintillators for neutron detection [22,23], or diamond based semiconductor detectors [24]. Gamma detection capabilities were added in the form of the LEAF system, an array of four scintillation based gamma spectrometers [16,25].…”

Section: Simultaneous In-core Neutron and Gamma Detectionmentioning

confidence: 99%

Delayed gamma fraction determination in the zero power reactor CROCUS

Pakari

Mager

Lamirand

et al. 2021

EPJ Nuclear Sci. Technol.

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Gamma rays are an inextricable part of a nuclear reactor’s radiation field, and as such require characterization for dose rate estimations required for the radiation protection of personnel, material choices, and the design of nuclear facilities. Most commonplace radiation transport codes used for shielding calculations only included the prompt neutron induced component of the emitted gamma rays. The relative amount of gamma rays that are emitted from delayed processes – the delayed gamma fraction – amount to a significant contribution, e.g. in a typical zero power reactor at steady state is estimated to be roughly a third. Accurate predictions of gamma fields thus require an estimation of the delayed content in order to meaningfully contribute. As a consequence, recent code developments also include delayed gamma sources and require validation data. The CROCUS zero power research reactor at EPFL is part of the NEA IRPhE and has therefore been characterized for benchmark quality experiments. In order to provide the means for delayed gamma validation, a dedicated experimental campaign was conducted in the CROCUS reactor using its newly developed gamma detection capabilities based on scintillators. In this paper we present the experimental determination of the delayed gamma fraction in CROCUS using in-core neutron and gamma detectors in a benchmark reactor configuration. A consistent and flexibly applicable methodology on how to estimate the delayed gamma fraction in zero power reactors has hitherto not existed – we herein present a general experimental setup and analysis technique that can be applied to other facilities. We found that the build-up time of relevant short lived delayed gamma emitters is likely attributed to the activation of the aluminium cladding of the fuel. Using a CeBr3 scintillator in the control rod position of the CROCUS core, we determined a delayed gamma fraction of (30.6±0.6)%.

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Section: Simultaneous In-core Neutron and Gamma Detectionmentioning

confidence: 99%

Delayed gamma fraction determination in the zero power reactor CROCUS

Pakari

Mager

Lamirand

et al. 2021

EPJ Nuclear Sci. Technol.

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“…The operation ionization chambers and the large fission chambers were operated in current mode [2], whereas all the other detectors were operated in pulse mode using spectrometry charge preamplifiers. The detectors and their electronics were connected to the ISTec, TUD, and both EPFL pulse and current mode instrumentations, with a number of detectors depending on the number of possible inputs [6].…”

Section: Neutron Detection Instrumentationmentioning

confidence: 99%

Neutron noise experiments in the AKR-2 and CROCUS reactors for the European project CORTEX

Lamirand¹,

Rais²,

Hübner³

et al. 2020

EPJ Web Conf.

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The present article gives an overview of the first experimental campaigns carried out in the AKR-2 and CROCUS reactors within the framework of the Horizon 2020 European project CORTEX. CORTEX aims at developing innovative core monitoring techniques that allow detecting anomalies in nuclear reactors, e.g. excessive vibrations of core internals. The technique will be mainly based on using the fluctuations in neutron flux, i.e. noise analysis. The project will result in a deepened understanding of the physical processes involved. This will allow utilities to detect operational problems at a very early stage, and to take proper actions before such problems have any adverse effect on plant safety and reliability. The purpose of the experimental campaigns in the AKR-2 and CROCUS reactors is to produce noise-specific experimental data for the validation of the neutron noise computational models developed within this framework. The first campaigns at both facilities consisted in measurements at reference static states, and with the addition of mechanical perturbations. In the AKR-2 reactor, perturbations were induced by two devices: a rotating absorber and a vibrating absorber, both sets in experimental channels close to the core. In CROCUS, the project benefited from the COLIBRI experimental program: 18 periphery fuel rods were oscillated at a maximum of ±2 mm around their central position in the Hz range. The present article documents the experimental setups and measurements for each facility and perturbation type.

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“…The description of CROCUS follows [2]. The CROCUS reactor is a two-zone, uranium-fueled, H 2 O-moderated critical assembly operated by the Laboratory for Reactor Physics and Systems Behaviour (LRS) at the Swiss Federal Institute of Technology Lausanne (EPFL).…”

Section: The Research Reactor Crocusmentioning

confidence: 99%

“…With a variety of experimental programs (e.g. [1], [2]) that so far only exploited neutron detection, the acquisition of gamma detectors intends to extend the capabilities of CROCUS.…”

Section: Introductionmentioning

confidence: 99%

Design and Simulation of Gamma Spectrometry Experiments in the CROCUS Reactor

et al. 2020

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Gamma rays in nuclear reactors, arising either from fission or decay processes, significantly contribute to the heating and dose of the reactor components. Zero power research reactors offer the possibility to measure gamma rays in a purely neutronic environment, allowing for validation experiments of computed spectra, dose estimates, reactor noise and prompt to delayed gamma ratios. This data then contributes to models, code validation and photo atomic nuclear data evaluation. In order to contribute to aforementioned experimental data, gamma detection capabilities are being added to the CROCUS reactor facility. The CROCUS reactor is a two-zone, uranium-fueled light water moderated facility operated by the Laboratory for Reactor Physics and Systems Behaviour (LRS) at the Swiss Federal Institute of Technology Lausanne (EPFL). With a maximum power of 100W, it is a zero power reactor used for teaching and research, most recently for intrinsic and induced neutron noise studies. For future gamma detection applications in the CROCUS reactor, an array of four detectors - two large 5”x10” Bismuth Germanate (BGO) and two smaller Cerium Bromide (CeBr3) scintillators - was acquired. The BGO detectors are to be arbitrarily positioned in the core reflector and out of the vessel for measurements at arbitrary distances. The CeBr3 detectors on the other hand are small enough to be set in the guide tubes of the control rods for in-core measurements. We present a study of the neutron and gamma flux in the core and reflector using the MCNP 6.2 and Serpent 2 Monte Carlo codes for coupled neutron and photon transport criticality calculations. More specifically, we investigate and compare predicted spectra as well as reactivity worth of different envisioned experimental setups. We further predict pulse height spectra as well as doses to the crystals with and without cadmium shielding to estimate allowable reactor powers with respect to detector radiation hardness. The results serve as basis for calibration and aid in the design and regulatory approval of the experiments.

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Kinetic Parameter Measurements in the CROCUS Reactor Using Current Mode Instrumentation

Cited by 20 publications

References 9 publications

Delayed gamma fraction determination in the zero power reactor CROCUS

Delayed gamma fraction determination in the zero power reactor CROCUS

Neutron noise experiments in the AKR-2 and CROCUS reactors for the European project CORTEX

Design and Simulation of Gamma Spectrometry Experiments in the CROCUS Reactor

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